1. Field of the Invention
This invention relates generally to pressure relief and pressure regulating valves, and more particularly to valve seals that minimize pressure gain with increasing flow in pressure regulator valves and the like, specifically well suited for use in fuel injection and other systems where minimizing pressure increases with increasing flow is desirable for improved system performance.
2. Description of the Prior Art
Internal combustion fuel injection systems typically require some form of pressure controlling device, either a pressure regulator or a pressure relief valve to maintain an appropriate fuel pressure at the injectors. Conventional fuel pressure relief valves and regulators utilize metal-to-metal seals in the pressure relief valve. The metal-to-metal sealing elements are resistive to surface depression of the adjacent sealing surfaces; resulting in a direct flow path with minimum pressure drop. However, the metal-to-metal seals are subject to high leakage rates as the two sealing surfaces are rigid, nonconforming and highly sensitive to the effects of contamination. One solution to this problem employs rubber sealing pressure regulator valves. Such fuel pressure regulator valves comprise a rubber sealing element which is held in intimate contact with a metal seat, the seat having a raised boss that contacts, and depresses into the surface of a planar rubber element. In such a traditional valve design the annular metal sealing surface contacts the relatively thick flat rubber pad to affect the valve seal. Because of the relative softness, and viscoelastic properties, of the rubber the metal ring causes a permanent indention into the rubber surface. This surface depression typically causes a permanent “compression set” in the rubber. As the valve begins to open, the fluid flow is constrained to conform to the complex channel defined by surface deformation in the rubber, which results in a labyrinth flow path as the pressure regulator valve begins to open. The long and convoluted flow path causes a significant pressure drop at initial valve opening.
Metal-to-metal sealed devices are more expensive and have a higher leak rate than rubber sealing pressure regulator valves. Leakage is typically associated with increased difficulty starting the associated vehicle. However, conventional rubber sealing pressure relief valves and regulators have a greater pressure drop, and less linear flow characteristics. These liabilities limit the application of rubber sealing pressure regulator valves.